The invention has particular, but not exclusive, application in the glassware industry where, for example, bottles are fed upright in a stream on a conveyor from a manufacturing machine. After manufacture, it is necessary for the bottles to be checked for flaws and this is normally effected by television scanner equipment, such as that sold under the Registered Trade Mark INEX. The scanner equipment is capable of dealing with bottles at a speed of up to 500/min, whereas modern manufacturing machines produce bottles at around only half that figure. Hence, to make more efficient use of the scanning equipment, it is desirable to produce more than one stream of bottles and feed them via the combiner, where they are guided by a controlled phasing to merge into a single stream before passing the scanning equipment.
A combiner is known in which each stream is controlled by a so-called "starwheel" and guide rails. Thus, for example, where the bottles are being fed in two streams to the combiner, a starwheel is provided for each stream and the two starwheels are provided on each side of a central guide rail. The starwheels each have a set of control elements, usually in the form of fingers, spaced around its periphery, the two starwheels being oppositely driven at the same speed to cause the control elements to act in the movement direction of the streams, said control elements being preset out-of-phase with each other and arranged for alternately controlling the spacing of the bottles from the two streams into the single stream.
Difficulties can arise because the speed at which the two streams of bottles enter the combiner can be different, even though the speed of the respective conveyors is the same. Thus, for example, a slightly different output and/or spacing of the bottles leaving their respective manufacturing machines may occur. Should this happen, then because the control elements of the two starwheels are preset in their out-of-phase positions, the bottles from the two streams can clash as they are being combined and perhaps cause breakages or other damage.